Now to the missing baby found because a quick-thinking gas station worker noticed the woman minding her was acting strangely and called the cops. Bazi kanani is here with the story. Reporter: This morning, a 6-month-old baby girl is safe, back at home are her mother. And her kidnapper behind bars. All because a convenience store clerk trusted her guts and called the police. How can I help you? I have a lady who broke down on the freeway. She's acting really weird. Reporter: Karen was working the cash register last Wednesday when 57-year-old Karen Ferguson came in with a baby. Atkins said Ferguson was acting strangely. Trying to feed the infant cappuccino and couldn't answer simple questions about the girl's name. That's when she dialed 911. I just, my gut is wrong. I don't know. No one is missing a baby, right? Not that I'm aware of. Reporter: But somebody was. 300 miles away. An amber alert issued earlier that day for 6-month-old lelani moseley, last seen with her grandmother. Karen Ferguson who is bipolar and off medication. She was able to keep the woman distracted until police arrived. It's a mom thing. If it wasn't her baby, it would kill me if I let her walk out that door and know later on that it wasn't hers and I could have done something at that moment. Reporter: This morning, police are thanking Atkins for her quick thinking. Had it not been for her and how observant she was, we probably wouldn't be standing here with a successful story right now. Reporter: Ferguson, the baby's grandmother, is being held in Arizona on $50,000 bail, booked on child endangerment, abuse, and custodial interference. She reportedly took the mother's child why she was sleeping. The gas station clerk is, herself, a mother. A mother's gut intuition. Exactly. You have a 9-month-old as well. Yes, and I know that cappuccino is not good. Let's to across the pond.

This transcript has been automatically generated and may not be 100% accurate.

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